90 IVemerian Natural History Society. 



some of the disciples of this illustrious man, who suppose 

 the metals to be compounds of hydrogen. 



Jan. 19 and 26. — A. Marsden, esq., Vice-president, in 

 the chair. Paxt of a long paper, illustrated with several draw- 

 ings by Mr. Troughton, mathematical instrument maker, 

 was read, describing his instruments and methods of gra- 

 duating quadrants, sectious of circles, and other instruments 

 for mathematical and philosophical experiments. Mr. Trough- 

 ton's theoretical method consists in making o\it a table of 

 errors, by which means he corrects the dots made on the 

 graduated circle, previous to the application of his instru- 

 ment for dividing it into 180 degrees. Of this instrument, 

 invented by his brother, and improved by himself, no cor- 

 rect idea can. be given without the drawings, which unfold 

 the whole secret of the author's superior mode of manufac- 

 turing mathematical instruments. 



WERNERIAN NATURAL HISTORY SOCIETY. 



At the meeting of this Society on the 14th of January, 

 Dr. Thomas Thomson read an interesting description and 

 analysis of a particular variety of copper-glance from North 

 America. 



At the same meeting Dr. John Barclay communicated 

 some highly curious observations which he had made on the 

 caudal vertebrae of the Great Sea Snake, (formerly men- 

 tioned) which exhibit in their structure some beautiful pro- 

 visions of Nature, not hitherto observed in the vertebrae of 

 any other animal. 



And Mr. Patrick Neill read an ample and interesting ac- 

 count of this new animal, collected from different sources, 

 especially letters of undoubted authority, which he had re- 

 ceived from the Orkneys. He stated, however, that owing 

 to the tempestuous season, the head, fin, sternum, and 

 dorsal vertebrae, promised some weeks ago to the University 

 Museum of Edinburgh, had not yet arrived ; but thaj; he 

 had received a note from Gilbert Meason, esq., (the gen- 

 tleman on whose estate in Stronsa the sea snake was cast,) 

 intimating that they might be expected by the earliest ar- 

 rivals from Orkney. In the mean time, he submitted to the 



Society 



